Question

if the nth term of AP 9,7,5....is same as the nth term of 15,12,9....Find n​

Answer 1

Answer:

$\implies{\mathsf{n = 7}}$

Step-by-step explanation:

Given:-

1st AP 9,7,5...

2nd A.P 15,12,9....

To Find : n

$\implies{\mathsf{A1_n = a_1 + (n-1)d_1}}$

$\implies{\mathsf{A2_n = a_2 + (n-1)d_2}}$

Now a/c to question:

$\implies{\mathsf{A1_n = A2_n}}$

$\boxed{\boxed{\underline{\underline{\bold{\mathsf{Apply\:Formula}}}}}}$

Put in the values:

$\implies{\mathsf{9 + (n-1)(-2) = 15 + (n-1)(-3) }}$

$\implies{\mathsf{-2n +11 = -3n + 18 }}$

$\implies{\mathsf{n = 7}}$

$\rule{200}{1}$

$\rule{200}{1}$

$\boxed{\boxed{\boxed{\underline{\underline{\bold{\mathsf{Formula\:Used}}}}}}}$:—

$\bigstar$$\implies{\mathsf{A_n = a + (n-1)d }}$